Previous and current methods of attacking surface targets from the air include visual bombing and strafing and the use of a limited number of guided missiles. Visual delivery of bombs and strafing has many disadvantages, among which are (1) large number of sorties required to defeat a target due to poor accuracy, (2) high attrition rate of friendly aircraft and (3) clear weather/daylight use only because of the visual sighting requirement.
Guided missiles such as Walleye and Bullpup are also visual, clear weather, daylight systems only and therefore, cannot be used at night and during inclement weather.
The Shrike and Standard ARM missiles are, for all practical purposes, all-weather systems. However, the passive guidance system associated with both is specific to various VHF and UHF point sources and does not have broad application. Basically the two missiles are anti-radar only.
The electric and magnetic fields due to low frequency power networks have been considered and it can be shown that at distances which are large compared with the dimensions of a network, but small compared with the critical distance .lambda./2.pi. = c/.omega., the electric and magnetic fields are essentially the same, respectively, as those due to an alternating electric dipole together with an alternating magnetic dipole of suitable complex vector moments located at an arbitrarily chosen interior point of the network. Here .lambda. is the wavelength, .omega. the angular velocity, and c the velocity of light. Unlike the situation with far field radiation, the electric and magnetic fields are essentially independent of each other -- each being determined by its own dipole; also, for practical purposes the distinction between networks lies entirely in differences in the vector moments of the corresponding dipoles.
This invention describes a method for determining the direction of a dipole using field data taken at a point in space; also two guidance methods are presented which may be used to make a missile home in on the dipole. In the first of these methods, the required data is given by two sensors -- one in the front of the missile, and the other in the rear. This data is adequate for homing purposes despite the fact that it is not sufficient to determine the direction of the dipole. In the second of these methods, the required data is obtained from four sensors placed at the tips of the four wings -- two lateral and two vertical -- of the missile. Although this data is sufficient to determine the direction of the dipole, this direction is not the one that is chosen for homing purposes.
In the case for each of these guidance methods, expressions are derived which give the error signals that would be obtained for a specified dipole, and with a specified position and orientation of the missile. This data can be used to investigate the feasibility, or calculate the performance of a given system, and also to indicate the required sensitivity of a proposed electronic and servo system.